The present invention generally relates to a data transmission system and, more particularly, to a data transmission system in which the data to be transmitted tend to be adversely affected by noises.
There is known a control system wherein the control unit including a motor, a heater or the like and operable to actually control the temperature and/or humidity in a control object or controlled system, and a controller including a display unit and a setting unit for setting the temperature and/or humidity are separated from each other. In this type, data transmission is carried out between the control unit and the controller, and since the control unit includes a source of noises such as a motor or the like, data that can be transmitted therebetween must be of a nature hard to affect adversely by noises.
Apart from the above, in the temperature and/or humidity control system, the data transmission speed may be relatively low since the temperature and/or humidity in the control object do not change so quickly. Although it can be contemplated to transmit such data by the use of a hard logic device or logic hardware, the setting and the contents that can be displayed are simplified and it is difficult to add various functions. In addition, where data to be transmitted are in the form of an analog signal, a transmission interface unit must have the capability of effecting an analog/digital conversion, and an error in transmission is likely to occur during the conversion.